Transporting hydrocarbons in a body of water involves a temperature drop due to the heat exchanges with the surrounding environment. Indeed, the hydrocarbons go from a temperature of about 50° C. to 150° C. in the reservoir to a temperature of around several degrees. This temperature drop may lead to an increase in the viscosity of the hydrocarbons, causing a decrease in the flow rate within the pipes or the formation of hydrates and paraffins, which often cause blockages of the pipes.
To offset this temperature drop, double-jacketed pipes (“pipe in pipe”) have been developed. In this type of conduit, the fluid is transported through an inner tube that is in turn located inside an outer tube providing passive thermal insulation.
This solution was improved by adding, to the passive thermal insulation, active heating of the conduits by winding heating cables directly around the inner tube (“Electrically Trace Heated Pipe-in-Pipe”, ETH-PiP).
However, such a solution is expensive and the steel double jacket of such a pipe represents a relatively heavy weight, which makes installation difficult, in particular at great depths.
An alternative solution making it possible to resolve these problems is described in document U.S. Pat. No. 6,940,054.
This document describes a thermally insulated tube surrounded by heating cables and electrical cables. The tube comprises thermal insulation means intended to reduce heat exchanges with the surrounding environment. The insulation means comprise inner and outer members wound around the tube. The outer and inner members form longitudinal channels making it possible to accommodate the heating cables. Around the outer insulating members, an outer strap is wound intended to keep the inner and outer insulating members around the tube.
In the manufacturing method described in U.S. Pat. No. 6,940,054 4B1, the very long insulating parts are wound in a spiral around the inner tube to form an insulation jacket.
The formation of the jacket by winding the insulating parts requires a rotating machine, allowing the insulating parts to be placed in a spiral, described in the document.
This type of device is very bulky and cumbersome. It is not possible to assemble the pipe on a site that does not have one, a fortiori on board a vessel for placing the rigid pipe.
Furthermore, some assembly sites are not configured to accommodate such a type of device. The assembly of a rigid pipe by such a method is therefore not possible on all assembly sites.
Lastly, these devices are expensive, as is building new sites suitable for receiving them.